The disclosed invention generally relates to liquid crystal light valve projectors, and is particularly directed to a liquid crystal light valve projector having an optical relay for imaging illumination at the light valves and an optical relay for imaging the light valve images.
The development of liquid crystal light valve (LCLV) technology has resulted in the development of large screen projectors which utilize one or more LCLV's to modulate the light being projected. The LCLV's are selectively modulated by respective appropriate apparatus such as cathode ray tubes (CRT's).
Color liquid crystal light valve projectors typically include color separating apparatus such as prisms or beamsplitters for separating white light into the three primary color bands; namely, red, green, and blue light components. The red, green, and blue components are individually modulated by respective light valves for projection. Examples of color LCLV projectors are set forth in U.S. Pat. No. 4,425,028, issued to R. J. Gagnon et al. on Jan. 10, 1984, and assigned to the assignee of this application; and in U.S. Pat. No. 4,461,542, issued to R. J. Gagnon on July 24, 1984, and also assigned to the assignee of the subject application.
Some known full color liquid crystal light valve projectors tend to be large in order to enclose the optical elements. For example, particular optical arrangements utilize both axes of polarization which requires placement of CRT light valve assemblies in different planes. Some optical arrangements may require larger optical elements or greater spacing between elements, which requirements may be in addition to the CRT light valve placement requirements. Regardless of the reason for size, if the LCLV projector is too large it may be inappropriate in applications where space is a premium, such as shipboard applications.
In addition to size considerations, the use of both axes of polarization is generally characterized by reduced contrast. The use of both axes of polarization may be an important consideration in some applications such as display systems generally known as "in-line infinity" display systems or "pancake window" display systems. In-line infinity display systems include polarizing elements and provide better transmission efficiency when illuminated with light having a single axis of polarization. Illumination with polarized light having both axes of polarization or with unpolarized light would result in a substantial amount of light being removed by a polarizer. Examples of in-line infinity display systems are referenced in a Farrand Optical Co., Inc. brochure M-1219B, November 1974.
A further characteristic of known liquid crystal light valve projectors is the typical utilization of illumination optics which provide image magnification to achieve the necessary telecentric illumination of the liquid crystal light valves. Such magnifying illumination optics may be less efficient and tend to impose limitations on the design of other elements of the projector, including the color separating apparatus.
Some known full-color liquid crystal light valve projectors utilize complex color separating apparatus which include optical grade oil as a refractive medium. The use of such oil requires the consideration of possible leakage, high cost, additional complexity, and increased weight. Also, some optical tanks require a particular orientation for proper operation.